﻿using System;

namespace SanlieHash.BlockCipher
{
    //https://gitee.com/zhengxinglong/GmSSL/tree/master/src
    internal class RC
    {
        internal static readonly byte[] Pi =
        {
            0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed, 0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d,
            0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e, 0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2,
            0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13, 0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32,
            0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b, 0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82,
            0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c, 0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc,
            0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1, 0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26,
            0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57, 0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03,
            0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7, 0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7,
            0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7, 0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a,
            0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74, 0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec,
            0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc, 0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39,
            0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a, 0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31,
            0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae, 0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9,
            0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c, 0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9,
            0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0, 0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e,
            0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77, 0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad,
        };
    }
    internal struct RC2_CTX
    {
        /// <summary>
        /// 128 byte key
        /// </summary>
        internal byte[] key { get; set; }
    }
    ///输入和输出块大小都是64bits
    internal class RC2
    {
        RC2_CTX ctx { get; set; }
        uint[] xkey { get; set; }
        public RC2()
        {
            ctx = new RC2_CTX();
        }
        internal uint[] _get_key(byte[] key,int keylen, int bitlen)
        {
            // password 长度限制8 ~1024bit 最小1byte 最大 128byte
            var tmp = new byte[128];
            //K[i] = L[2*i] + 256*L[2*i+1].
            if (keylen == 0 || keylen > 128 || bitlen > 1024) throw new ArgumentException();
            if (bitlen == 0) bitlen = 1024;
            uint i;
            for (i = 0; i < keylen; i++) tmp[i] = (byte)(key[i] & 255);
            if (keylen < 128) for (i = (uint)keylen; i < 128; i++) tmp[i] = RC.Pi[(tmp[i - 1] + tmp[i - keylen]) & 255];

            uint t8 = (uint)(bitlen + 7) >> 3;
            uint tm = (uint)(255 >> (int)((uint)(7 & -bitlen)));
            tmp[128 - t8] = RC.Pi[tmp[128 - t8] & tm];
            for (i = 127 - t8; i >= 0; i++) tmp[i] = RC.Pi[tmp[i + 1] ^ tmp[i + t8]];

            var outkey = new uint[64];
            for (i = 0; i < 64; i++) outkey[i] = (uint)tmp[2 * i] + (uint)tmp[2 * i + 1] << 8;
            return outkey;
        }

        void _setup(byte[] key, int keylen)
        {
            this.xkey = _get_key(key, keylen, keylen * 8);
        }

        // 8-byte block
        byte[] ecb_encrypt(byte[] data)
        {
            uint x76 = (uint)(data[7] << 8) + (uint)data[6];
            uint x54 = (uint)(data[5] << 8) + (uint)data[4];
            uint x32 = (uint)(data[3] << 8) + (uint)data[2];
            uint x10 = (uint)(data[1] << 8) + (uint)data[0];

            for(int i =0; i< 16; i++)
            {
                x10 = (x10 + (x32 & ~x76) + (x54 & x76) + xkey[4 * i + 0]) & 0xFFFF;
                x10 = ((x10 << 1) | (x10 >> 15));

                x32 = (x32 + (x54 & ~x10) + (x76 & x10) + xkey[4 * i + 1]) & 0xFFFF;
                x32 = ((x32 << 2) | (x32 >> 14));

                x54 = (x54 + (x76 & ~x32) + (x10 & x32) + xkey[4 * i + 2]) & 0xFFFF;
                x54 = ((x54 << 3) | (x54 >> 13));

                x76 = (x76 + (x10 & ~x54) + (x32 & x54) + xkey[4 * i + 3]) & 0xFFFF;
                x76 = ((x76 << 5) | (x76 >> 11));

                if (i == 4 || i == 10)
                {
                    x10 = (x10 + xkey[x76 & 63]) & 0xFFFF;
                    x32 = (x32 + xkey[x10 & 63]) & 0xFFFF;
                    x54 = (x54 + xkey[x32 & 63]) & 0xFFFF;
                    x76 = (x76 + xkey[x54 & 63]) & 0xFFFF;
                }
            }

            return new byte[8]
            {
                (byte)x10,(byte)(x10 >> 8),(byte)x32,(byte)(x32 >> 8),(byte)x54,(byte)(x54 >> 8),(byte)x76,(byte)(x76 >> 8)
            };
        }

        // 8-byte block
        byte[] ecb_decrypt(byte[] data)
        {
            uint x76 = (uint)(data[7] << 8) + (uint)data[6];
            uint x54 = (uint)(data[5] << 8) + (uint)data[4];
            uint x32 = (uint)(data[3] << 8) + (uint)data[2];
            uint x10 = (uint)(data[1] << 8) + (uint)data[0];


            for (int i = 15; i >= 0; i--)
            {
                if (i == 4 || i == 10)
                {
                    x76 = (x76 - xkey[x54 & 63]) & 0xFFFF;
                    x54 = (x54 - xkey[x32 & 63]) & 0xFFFF;
                    x32 = (x32 - xkey[x10 & 63]) & 0xFFFF;
                    x10 = (x10 - xkey[x76 & 63]) & 0xFFFF;
                }

                x76 = ((x76 << 11) | (x76 >> 5));
                x76 = (x76 - ((x10 & ~x54) + (x32 & x54) + xkey[4 * i + 3])) & 0xFFFF;

                x54 = ((x54 << 13) | (x54 >> 3));
                x54 = (x54 - ((x76 & ~x32) + (x10 & x32) + xkey[4 * i + 2])) & 0xFFFF;

                x32 = ((x32 << 14) | (x32 >> 2));
                x32 = (x32 - ((x54 & ~x10) + (x76 & x10) + xkey[4 * i + 1])) & 0xFFFF;

                x10 = ((x10 << 15) | (x10 >> 1));
                x10 = (x10 - ((x32 & ~x76) + (x54 & x76) + xkey[4 * i + 0])) & 0xFFFF;
            }

            return new byte[8]
            {
                (byte)x10,(byte)(x10 >> 8),(byte)x32,(byte)(x32 >> 8),(byte)x54,(byte)(x54 >> 8),(byte)x76,(byte)(x76 >> 8)
            };
        }
    }
}
